Automatic transmissions with a plurality of shiftable gears, without group shifting, are known in many examples. DE 199 12 480 A1 discloses a generic automatic transmission with three single spider planetary gear sets as well as three brakes and two clutches for shifting, thus allowing six forward gears and one reverse gear. For motor vehicles, this provides a very well adapted gear-change shifting as well as a good start-up ratio in the forward direction. The individual gears are achieved by selective closure of, at each time, two of the six shifting elements, so that for the gear transfer from the presently used ratio to another, either higher or lower, respectively only one shifting element need be opened and another shifting element closed.
As this is done, one input drive shaft of the automatic transmission is continually bound through a sun gear of the second planetary gear set. Further, the input drive shaft can be bound by means of the first clutch with a sun gear of the first planetary gear set and/or by means of the second clutch with a spider of the first planetary gear set. Additionally, or alternatively, the sun gear of the first planetary gear set can be bound by means of the second brake with the housing and/or a sun gear of the third planetary gear set by the third brake with the housing.
For the kinetic coupling together of the individual planetary gear set, DE 199 12 480 A1 describes two different versions. In the first version, provision has been made, that an output drive shaft of the automatic transmission is continually engaged with a spider of the third planetary gear set and with an internal gear of the first planetary gear set. The input drive shaft and the output drive shaft can, in this construction, be both placed coaxial to one another on opposite sides of the transmission housing as well as axis/parallel on the same side of the transmission housing. In the second version, provision has been made, that the output drive shaft is continually engaged with the spider of the second planetary gear set and with the internal gear of the first planetary gear set, also that the spider of the first planetary gear set is continually bound with the internal gear of the third planetary gear set, and that the internal gear of the second planetary gear set is continually engaged with the spider of the third planetary gear set. A construction of this type is particularly adaptable for a coaxial arrangement of the shafts for input and output.
Giving now consideration to the spatial arrangement of the planetary gear set, DE 199 12 480 A1 now proposes, that the three planetary gear sets be placed coaxially in a sequence, one next to the other, whereby the second planetary gear set appears axially between the first and the third planetary gear set. Further as to the spatial arrangement of the individual shifting elements, relative to one another and relative to the planetary gear sets, DE 199 12 480 A1 also suggests, that the first and the second brake are continually placed next to one another, whereby the second brake is always directly placed axially proximal to the first planetary gear set, and the third brake is always on that side of the planetary gear set which is remote for the third planetary gear set. With the arrangement, the two clutches are continually located directly beside one another. In a first arrangement variant, both clutches are upon that side of the third planetary gear set which is on the remote side of the first planetary gear set. In this way, the first clutch is axially directly bordering on the first brake and is closer to the first planetary gear set than is the second clutch. In connection with a non-coaxial location of the input drive shaft and the output drive shaft, in a second arrangement variant, the proposal is, that both clutches be placed on the remote side of the third planetary gear set, whereby, the second clutch is closer to the third planetary gear set than is the first clutch, and is axially located on output drive shaft active end, which placement, once again, places it on that side of the third brake which is remote side from the third planetary gear set.
The present invention, thus has the purpose of presenting an alternate arrangement of components for the automatic transmission made known as the state of the technology by DE 199 12 480 A1, wherein the most compact transmission assembly is made possible and in the longitudinal direction of the said transmission the design is most space saving. Preferably, the automatic transmission is designed to find application in a motor vehicle with a standard input drive and coaxially aligned drive shafts for input and output. Conversely, however, by means of the most relatively simple modifications the design can be used for non-coaxial input and output drive shafts.